President Trump's sudden decision to fire FBI Director James Comey on Tuesday was a genuine bombshell from an administration that seems to produce one on a daily basis. Nobody should shed any tears for Comey, who deserved his fate. But the real reason he was fired should make Americans more than a little nauseous.

The irony of the firing is that according to its stated reasons, it was eminently justified. In a letter explaining the firing, Deputy Attorney General Rod Rosenstein wrote: "I cannot defend the director's handling of the conclusion of the investigation of Secretary Clinton's emails, and I do not understand his refusal to accept the nearly universal judgment that he was mistaken." Rosenstein's argument is very strong.

Comey's decision to send a letter informing Congress that the investigation into Hillary Clinton's email server had been temporarily reopened violated departmental norms and rules, as well as the wishes of his superiors. Like his similarly inappropriate editorializing after he announced that he would not recommend that Clinton be charged with a crime in July, the letter was grossly prejudicial, creating the impression that Clinton might be guilty of severe wrongdoing, when in fact it was quickly determined that the emails discovered on Anthony Weiner's laptop contained no relevant evidence. The rules that Comey violated were in place exactly to prevent the kind of interference with an election that his letter constituted.

Even worse, it was revealed Tuesday that Comey greatly misstated the number of Clinton-related emails that had been forwarded to Weiner by his wife, top Clinton aide Huma Abedin. Comey claimed last week that "hundreds or thousands" of emails had been forwarded to Weiner, but in fact it was only a "small number." This makes it even harder to understand why he didn't just wait for the investigation to conclude before informing Congress. And it also makes it hard to escape the conclusion that his violation of the rules was motivated in part by bias against Clinton (however unconscious).

The evidence overwhelmingly suggests that had Comey not sent the letter on Oct. 28, Trump wouldn't be in a position to fire him. But whether or not he changed history, Comey's misconduct was a fireable offense. So what's the problem?

The Trump administration citing Comey's indefensible interference in the election as the reason for firing him essentially amounts to trolling. As Adam Serwer of The Atlantic points out, Attorney General Jeff Sessions had previously argued that Comey had an "absolute duty" to send the October letter. It's pretty hard for an action to be an "absolute duty" in October and a reason to fire someone in May. Trump also effusively praised Comey's decision to send the letter. And, indeed, Trump reportedly told Sessions to start looking for a pretext to fire Comey last week, although the problems with his actions during the campaign were well known. The idea that Trump fired Comey because he was unfair to Hillary Clinton doesn't pass the straight face test.

The real reason is almost certainly Trump's desire to stop the FBI's investigation into Russia's attempts to influence the election, possibly in collaboration with members of Trump's campaign. Many Democratic officeholders are calling for an independent prosecutor, arguing that Trump's new FBI director is highly likely to hamstring or end the investigation into Russian electoral interference and its ties to the Trump campaign. It's very hard to disagree.

Firing Comey removes one of the few remaining meaningful checks on Trump's power. Having a Trump lackey heading the FBI will not only damage or end the investigation into the vital question of Russian attempts to influence the election. It will also make it less likely that the FBI will vigorously investigate any ongoing or future scandals involving an administration with unprecedented conflicts of interest and an open contempt for basic rules and norms.

When Richard Nixon infamously fired special prosecutor Archibald Cox, it didn't save him from being forced to resign over Watergate because Republican legislators refused to look the other way. We now live in a different, and more dangerous, world.

With the Republican Congress having clearly signaled that it will not conduct meaningful oversight of the Trump administration, this represents a political crisis. Trump has sent a message about what will happen to anyone who threatens to stand up to him. It's hard to imagine this ending well.